1. Field of the Invention
The invention relates generally to carbon foam metal matrix composite materials. More particularly, the invention relates to drilling mud pumps that employ carbon foam metal matrix composites as reinforcing materials to enhance durability and operating lifetime.
2. Background of the Technology
To obtain hydrocarbons such as oil and gas, boreholes are drilled by rotating a drill bit attached to a drillstring. The drill bit is typically mounted on the lower end of the drillstring as part of a bottomhole assembly (BHA) and is rotated by rotating the drillstring at the surface or by actuation of downhole motors or turbines, or by both methods. With weight applied to the drillstring, the rotating drill bit engages the earthen formation and proceeds to form a borehole along a path toward a target zone.
During drilling operations, drilling fluid, or “mud” as it is also known, is pumped down through the drill string and into the hole through the drill bit. The drilling fluid exits the drill bit through nozzles or jet assemblies positioned in bores formed in the body of the bit. Drilling fluids are used to lubricate the drill bit and keep it cool. The drilling mud also cleans the bit, balances pressure, and carries sludge and formation cuttings created during the drilling process to the surface.
Pumps, typically referred to as slush or mud pumps, are commonly used for pumping the drilling mud. Such pumps used in these applications are typically reciprocating pumps of the duplex or triplex type. A duplex pump has two reciprocating pistons that each force drilling mud into a discharge line, while a triplex reciprocating pump has three pistons that force drilling mud into a discharge line. These reciprocating mud pumps can be single acting, in which drilling mud is discharged on alternate strokes, or double acting, in which each stroke discharges drilling mud.
In most mud pumps, a connecting rod extends between each piston and a reciprocating member that drives the movement of the piston within the corresponding cylinder. In some cases, an insert disposed in a mating recess of the reciprocating member pivotally supports the end of the connecting rod coupled to the reciprocating member. The insert also supports axial loads that are transferred between the reciprocating member and the piston via the connecting rod. A lubrication passage is provided in the reciprocating member and the insert to provide lubrication to the interface between the insert and the end of the connecting rod. In such pumps, the connecting rod is often made from hardened steel, the reciprocating member is often made from cast steel, and the insert is often made from bronze. Friction from the sliding engagement of the connecting rod and the insert during pumping operations creates heat that, over time, can detrimentally affect the insert, and hence the connection between the rod and the reciprocating member. For example, the combination of thermal stress and axial loads may induce cracking in the insert, particularly at the lubrication passage of the insert. Such cracks may propagate and increase in size over time, potentially leading to failure of the insert and/or damage to the mud pump.
Accordingly, there remains a need in the art for improved materials for supporting loads between a connecting rod and a reciprocating member of a mud pump. Such materials would be particularly well-received if they offered the potential to reduce friction and resulting heat between the connecting rod and the insert, and enhance the durability of the connection between the reciprocating member and the connecting rod.